Live feeds are commonly used in shrimp larval rearing to postlarval stage (Figure 24). Penaeid larvae are commonly reared on live unicellular algae during the protozoea stages. Algae are readily consumed from zoea 1 until about postlarvae (PL) 2. Tetraselmis suecica can be viewed in the gut up to PL2 in P. monodon and Fenneropenaeus indicus (Evans, 1992). Commercial algal species of the correct size and nutritional profile include the phytoflagellates Tetraselmis suecica, T. chuii and Isochrysis sp. and the diatoms Skeletonema costatum, Thalassiosira weissflogii, T. pseudonana, Chaetoceros gracilis, C. muelleri and C. calcitrans (FAO, 1985a,b; Kumlu, 1997a,b, 1998). Chaetoceros muelleri promotes good survival, weight gain and development to mysis 1 and PL2 (D’Souza et al., 2002; Pina et al., 2006). The target density for algae such as C. muelleri or S. costatum is 100 000 cells/ml as the only algae fed.  

As well as daily feed, water exchanges are applied to maintain the necessary water quality (Table 3). Feed and water exchange schedules vary in each hatchery according to the manager’s preferences.

Live or frozen animal prey such as Artemia nauplii are added along with algae during the mysis and early postlarval stages (Table 3).

Other forms of live animal feed can also give good results. Farhadian, Yusoff and Arshad (2007) and Farhadian et al. (2009) showed that P. monodon larvae at PL3 to 6 and PL9 to 12 can ingest Apocyclops copepodids selectively better than Artemia at 1:1 ratio, as shown by the improved body dry weight of the larvae. The copepod Apocyclops dengizicus (85–120 μm, 1.2 μg dry weight) is found in marine tropical shrimp ponds and can be considered as a good replacement for Artemia in penaeid larvae culture, as it has high nutritional value (Farhadian, 2006). Various formulated feeds and freeze-dried or frozen zooplankton (e.g. “Cyclopeeze”) are also used as supplemental feeds during larval rearing.

Guillards F/2 medium, later slightly modified as the L1 medium, is commonly use in the mass production of marine algae. Guillard's media suits mass cultures in columns. In tanks, it is not generally possible to achieve the same density, as the algae shades itself beyond a few centimeters depth, causing light limitations to growth (Augusti, 1991). The nutrient medium can therefore be reduced to F/4 in tanks (Uddin and Zafar, 2006). Silicate is only needed for diatoms.

Together with the nutrient requirements of shrimp, it is imperative to know the proximate composition of feedstuffs so as to be able to formulate a diet to meet these needs (Table 13a). The moisture content, crude protein, crude lipid, crude fibre, nitrogen-free extract (digestible carbohydrates), ash content, vitamins and minerals, available phosphorus, amino acid content and levels of polyunsaturated fatty acids of the n–3 and n–6 series should be known for each feed ingredient (Piedad-Pascual, 1988). Each raw material will have a different amino acid balance and in formulating a feed, the ingredient mix selected needs to satisfy the requirements of the shrimp. When compared with fishmeal, the raw material that is being replaced in most cases, plant proteins can be deficient in key amino acids (Table 15).

A combination of feed ingredients is needed to supply the nutrients and energy shrimp need for best growth. Commercial shrimp feeds contain a mixture of feedstuffs and vitamin and mineral premixes that provide the essential nutrients and energy. The percentage inclusion of each feed ingredient is determined by factors such as shrimp nutrient requirements, ingredient cost, availability of each ingredient, feed digestibility and processing characteristics (Tables 13a and 13b).

The major components of a typical 35 percent protein shrimp diet are wheat flour (35 percent), soybean meal (20 percent) and fishmeal (25 percent) (Hunter and Chamberlain, 2006) and perhaps yeast. These ingredients provide the protein, amino acids and energy in the diet. Protein supplements are sourced from animal, yeast or plant proteins. Animal proteins used in animal feeds come from inedible tissues from meat packing or rendering plants, milk products and marine sources. Those used in shrimp feed include marine fishmeals, shrimp waste meal, krill, squid meals and clam or scallop meal. Marine animal proteins are generally considered to be of higher quality than plant proteins. Marine animal proteins can be partly replaced by plant proteins in shrimp feeds without affecting growth and feed efficiency. Raw materials that have proven to be excellent major protein sources for shrimp diets include squid, soybean meal, shrimp meal and fishmeal (New, 1976).

Marine shrimp aquafeed diets included 35 percent fishmeal content in 1995 and 25 percent in 2000 (Tacon, 1998). Venero, Davis and Lim (2008) estimated that commercial shrimp feeds in 2007 contained approximately 25 percent fishmeal. Fish oil inclusion was 3 percent of the diet in 1995 and 2 percent in 2000. Other marine meals commonly included in shrimp diets are krill, shrimp, squid and scallop waste. These are considered as excellent source of high-quality proteins, highly unsaturated fatty acids, mineral and attractants (Venero, Davis and Lim, 2008).

Fishmeal is a major protein source in shrimp feeds. Commercial shrimp diets typically contain approximately 25 percent fishmeal (Tacon and Barg, 1998). Fishmeal is a rich source of high-quality protein, has relatively high energy content and is rich in important minerals such as phosphorus, B vitamins and essential fatty acids.

Fishmeal can become rancid, and quality/freshness is affected by many factors. Ricque–Marie et al. (1998) found that fresh fishmeal gave better growth in all shrimp species tested, including P. monodon.

Fish oils provide essential fatty acids required by shrimp (Table 13a). Fish and squid oils are used in shrimp and prawn feeds. Squid oil is available from the Republic of Korea, while fish oil is comes largely from the Americas (FAO, 2007b), but can also be sourced from countries like South Africa.

This ingredient is used as a binder in pelleted shrimp feeds (FAO, 2007b). Pelleted feeds require a minimum of 20 percent starch from cereal grains to improve water stability (Chamberlain and Bortone, 2006). Ideally, wheat should have high gluten content. Gluten is responsible for the elasticity and extensibility characteristics of flour dough and affects the binding properties of the wheat flour. Wet gluten reflects protein content and is a common flour specification required by end-users in the shrimp industry. Indian wheat has a low wet gluten index (<28 percent) relative to the ideal index for shrimp feed pelleting (32 percent) (Suresh, 2007). A high protein product with strong gluten wheat is about 35 percent, while 23 percent is for low protein, weak gluten wheat (AACC, 2000). The wet gluten test provides information on the quantity and estimates the quality of gluten in wheat or flour samples. Wheat gluten as a product from wheat is often added as a binder to shrimp feeds (see below).

Shrimp feeds need to be water stable and sink. Feed formulations need to include this as a factor in the selection of suitable ingredients. Binders are often used to achieve the necessary water stability (Lim and Cuzon, 1994; Hunter and Chamberlain, 2006). Urea formaldehyde, wheat gluten and gelatin are common binders used in shrimp feed (Table 6). High-gluten wheat flour is commonly used as the starch source with good binding properties or where this is not available; wheat gluten with available wheat flour is added as the binder for shrimp feeds.

Crustacean or krill meal are good feed attractants at 50 g/kg (Smith et al., 2005), especially for feeds that contain low levels of fishmeal and relatively high levels of plant proteins. Products like crab meal, krill meal, shrimp head meal and shrimp shell meal are included at about 3 to 5 percent of feed mass (Hunter and Chamberlain, 2006).

Krill oil and meal are high in omega-3 bound phospholipids and astaxanthin. At an 11 percent inclusion of krill in the diet, fishmeal can be significantly reduced, fish oil at least halved and soya lecithin and cholesterol excluded from shrimp formulations, going by research with P. vannamei, where the krill diet was cheaper (Baevre-Jensen and Nunes, 2008). The cost of krill needs to be offset against these savings.

Squid liver powder (1–3 percent), squid meal (1–3 percent), fish hydrolysates (2–5 percent) and fish solubles (2–5 percent) can all serve as attractants. Squid products have good amino acid and fatty acid profiles and are a shrimp growth promoter (Hunter and Chamberlain, 2006).

Hunter and Chamberlain (2006) listed the use of enzymes, growth promoters, health additives (immunostimulants, probiotics, vaccines) and toxin absorbers, but none of these are widely or standardly incorporated or well researched at present. Commercial synthetic antioxidants and mould inhibitors are added to feeds (Table 6).

Refer to Feed Machinery for an example of the equipment used in a feed mill. The shrimp pelleting technology is described by Tan and Dominy (1997).

The feed specifications of Akiyama, Dominy and Lawrence (1991) are still safe and valid levels. Conklin (2003) observed that the shrimp requirement for specific amino acids still requires research. Table 13a shows typical feedstuffs used in shrimp feeds. This list will differ locally as well as nationally, and the percentage inclusion of feedstuffs will be species specific. Some nutritional interests, deficiencies and processing restrictions in selected raw materials are listed in Table 13b. Table 12a has suggested feed quality norms for Penaeus monodon. Table 4 has examples of practical feed formulations for P. monodon. Table 5 has some examples with specifications for commonly used commercial feed for P. monodon.